Jet refrigerating system with osmotic pump



Jan. 11,1938.

K. P. BRACE ET AL JET REFRIGERATING SYSTEM WITH OSMOTIC PUMP Filed April 19, 1935 4 Sheets-Sheet l Summon 1 11 emper]? Brace RollerzB @razdara' (Ittorneg Jan. 11, 1938. K, BRACE ET AL 2,104,847

JET REFRIGERATING SYSTEM WITH OSM OTIC PUMP Filed April 19, 1955 4 Sheets-Sheet 2 v ZSnventord HemperPBraae 3g flake/"51? raw 0111 Gttorneg Jah. 11, 1938. K. P. BRACE ET AL 2,104,847

JET REFRIGERATING SYSTEM WITH OSMOTIC PUMP Filed April 19, 1935 4 Sheets-Sheet 3 Zinnentoro Gum-neg Jan. 11, 1938. K. P. BRACE ET AL JET REFRIGERATING SYSTEM WITH OSMOTIC PUMP 4 Sheets-Sheet 4 Filed April 19, 1935 3 nnentord 5 an? Brace R0 K P mwford (Ittorneg [rm be?" Patented Jan. 11, 1938 ATEN'E' @FFiCE JET REFRIGERATING SYSTEM WITH OSMOTIC PUMP Kemper P. Brace and Robert B. P. Crawford,

Washington, I). O.

Application April 19, 1935, Serial No. 17,369

11 Claims.

This invention relates to refrigerator systems of the jet compressor type. Its object is to pro--, vide a heat operated system of this type which is simple in construction and which has no moving parts for conveying the'refrigerant from a region of low pressure toa region of high pressure.

The system makes use of the jet or aspirator principle in which a jet of vapor is delivered at high velocity thru a nozzle and the vacuum created at the nozzle is employed to draw evaporate d refrigerant from the evaporator. The entrained and the entraining gas are brought together after passing the jet stage and are condensed.

It is obvious that the pressure in the boiler must be greater than the pressure in the condenser and receiver. But it is necessary that the refrigerant be continuously returned to the boiler if the system is to operate continuously. One of the purposes of this invention is to effect this return of the refrigerant to the boiler against this higher pressure in the boiler and to do this without the use of mechanical pumps or other mechanical moving parts.

This invention is based on the known fact that, if a solution of a nonvolatile solute in a solvent is separated from the pure solvent by a semi-permeable membrane, the pure solvent will fiow by osmosis into the solution thru the membrane unless the pressure of the solution is high enough to prevent it. The pressure necessary to prevent the above mentioned flow iscalled the osmotic pressure of the solution. The osmotic pressure of most solutions is very high. The osmotic pressure of a 6 molar aqueous sugar solution, for example, is about 3410 lbs. per square inch. If, therefore, a six molar aqueous sugar solution is separated from pure water by means of a semi-permeable membrane, a pressure of 3410 lbs. per square inch'would have to be applied to the solution to prevent the water from flowing into the solution thru the membrane. Practical experiments have shown that the rate of flow of a solvent into a solution thru a membrane which is semi-permeable is quite rapid, and since the osmotic pressures are so high, moderate pressure differences between the solution and the solvent do not appreciably affeet the rate of flow.- The principle of osmosis, therefore, afiords a simple and rapid method of pumping a solvent from a region of low pressure to a region of high pressure without moving parts.

Further objects and advantages of the invention will'become apparent from the description which follows.

Referring to the accompanying drawings which are made a part hereof, and on which similar reference characters refer to the same parts throughout,

Figure 1 is a view in elevation, with parts shown in section, showing my system,

Figures 2 and 3 are detail views of a modified form of membrane which may be used in the system,

Figure 4 is a view in elevation of a slightly modified form of system,

Figure 5 shows a modified form of control of the circulation of the refrigerant,

'Figure 6 is a still further modified form in which a semi-permeable membrane separates the pure solvent from the boiler and from the evaporator,

Figure 7 is a view similar to Figure 1 but with a float controlled valve for regulating the flow of refrigerant to the evaporator, and

Figure 8 is a view similar to Figure 'l with a pressure controlled refrigerant circulating valve.

In the drawings numeral Ill indicates a boiler having therein a body of refrigerant I2, the composition of which will be later explained. A suitable heater I3 is positioned beneath the heater for boiling ofl the refrigerant. A pipe I4 conducts the stream of vapor from the boiler toa nozzle I! which projects into a chamber II. The chamber II is connected by a pipe IS with an evaporator H. The evaporator is kept partially filled with refrigerant I 8. A pipe l9 conducts the motive vapor from nozzle i5 and the entrained vapor from pipe Hi to a chamber 20 where it is condensed by suitable cooling means here shown as an air cooling system made up of a plurality of fins 2|. Pure solvent 22 in a receiver is separated from the body of the solu- 'tion l2 in the boiler by a semi-permeable membrane 23. In order to prevent too great heat loss from the boiler to the solvent 22 in'the receiver a relatively long pipe 24 is used to conduct the refrigerant from the receiver to the boiler. A pipe 25 conducts pure solvent from the body of solvent 22 to the evaporator ll.

Before starting operation the whole system is purged as far as possible of all air and other foreign gases. A device 26 filled with a suitable substance is provided for absorbing carbon dioxide, oxygen and nitrogen. Since air and other non-condensable gases are removed from the system, the pressures existing in the system above the liquid in the boiler, in the evaporator and in the receiver are the pressures of the liquids at the temperatures involved. Since the temperature in the condenser 20 is higher than in the evaporator I I, the pressure on the body'of refrigerant 22 is greater than the pressure in the evaporator. the evaporator I1 is positioned at a greater height than the condenser. This height must be great enough for the hydrostatic head in the evaporator to equal the greater pressure in the receiver.

With the evaporator positioned at the proper height there will be an equilibrium between the weight of the column of liquid represented by the difference in height of the evaporator and the pressure in the receiver. When equilibrium has been reached, any refrigerant drawn oil! from the evaporator and condensed in the condenser will reduce the level in the evaporator and increase it in the receiver, hence refrigerant will flow from the receiver thru pipe 25 to the evaporator.

In order for refrigerant vapor to flow at high velocity from the boiler to the nozzle I5 so as to entrain vapor from the evaporator H, the pressure in the boiler must be considerably greater than-the pressure in the condenser. This means that refrigerant must be boiled off at a rapid rate. But in order to maintain a continuous cycle the refrigerant boiled off must be replaced and this replacement must be effected against the high pressure in the boiler. This is accomplished by adding a non-volatile solute to the refrigerant to form a solution in the boiler and separating the solution in the boiler from pure solvent in the receiver by the semi-permeable membrane 23.

The jet cycle is effective only when the refrigerants used exert fairly low vapor pressures. Examples of such refrigerants are water, carbon tetrachloride, ether, alcohol, trielene, dielene, chloroform, carrene, etc. The refrigerant in the condenser 20 and in the evaporator l'l could be any one of the media mentioned. The solution in the boiler could be any non-volatile solute dissolved in any of the media mentioned to form a solution. Examples of such non volatile solutes 'are sugar, as mentioned above, or lithiumchloride.

The semi-permeable membrane could be any.

membrane permeable to therefrigerant but not permeable to the solute dissolved in the solution. Suitable examples of such membranes are collodion, parchment, animal intestine, animal bladder, fish skin, rubber, copper ferrocyanide precipitated in porous earthenware, porcelain, ground glass, gelatine, etc. All of these membranes are permeable as to water but impermee' able as to sugar and lithium chloride when these are dissolved in water.

The semi-permeable membrane might be in any suitable form, such as a corrugated sheet 21 shown in Figure 2 or a series of tubes in parallel as shown at 28 in Figure 3, or in any other suitable shape so as to increase the superficial area sufliciently to effect the pumping action.

In operation, heat is applied to the boiler i0 so as to build up a pressure therein to produce a jet of refrigerant issuing from the nozzle 85. This reduces the pressure above the refrigerant in the evaporator ii and induces more rapid evaporation. The entrained and the entraining vapors are condensed in 20 and collect in receiver 22 as pure solvent liquid. The pressure in the receiver is greater than the pressure in the evap- In order to balance the pressures,v

orator so that refrigerant is forced thru the pipe 25 into the evaporator until there is an equilibrium between the pressure in the receiver and the hydrostatic pressure of the liquid in the pipe 25 due to the greater elevation of the evaporator above that of the receiver.

Due to the tendency of pure solvent from receiver 22 to flow into the solution E2 in the boiler there will be a steady-flow of solvent .into the boiler, because the osmotic pressure causing the flow may be of the order of 3000 lbs. per square inch, depending on the concentration of the solution, while the actual pressure difference between the boiler and the receiver in the opposite direction would be of the order of from '10 to 30 lbs. per square inch, depending on the nature of the refrigerant used in the cycle.

The system shown in Figure 4 difiers from that shown in Figure l in that a force other than that due to the hydrostatic head in the evaporator is used to regulate the flow of condensed refrigerant into the evaporator, when, for' instance, the refrigerant is of such a nature that an extremely high pressure difference. exists between the hlgh'side and the low side. In this modification, the liquids in boiler 30 and evaporator 29 are respectively a solution of a nonvolatile solutein a volatile solvent and a more concentrated solution of the same nature. The concentrated solution in the evaporator 29 is separated from the dilute solution in the boiler 30 by means of a semi-permeable membrane 88, and the dilute. solution in the boiler 30 is separated from the pure solvent in the condenser Si. by another semi-permeable membrane 3. The operation is as follows: Due to osmotic pressure the pure solvent in condenser 3i passes thru the membrane 3 into the boiler 30. Since the concentration of the solution in the boiler 30 is less than the concentration of the solution in the evaporator and since the osmotic pressure of a solution is proportional to the concentration of the solution pure solvent will flow from boiler 30 into evaporator 29 thru the semi-permeable membrane 33. The rates of fiow thru mem branes 3 and 33 can be predetermined at proper values by regulating the initial concentrations of the solutions in boiler 30 and evaporator 20 and the surface area. of the membranes 8 and 38.

In Figure 5 a valve 36 controlled by a float 3a which is responsive to the changing level of the refrigerant in the evaporator 3i controls flow of refrigerant from the body of pure solvent 40 thru the pipe 39 into the evaporator. In this installation the evaporator may be placed at the same level as the boiler and condenser and receiver. The greater pressure in the receiver will force liquid from. the receiver into the evaporator and the valve will control this flow.

In Figure 6 a pipe M connects the body of pure solvent 42 with the evaporator 53. The evaporator contains a solution 45 of a non-volatile solute in a volatile solvent or refrigerant. A semipermeable membrane 44 in the pipe M separates the solution in the evaporator from the pure solvent Q2. As the concentration of the solution in the evaporator is increased due to the evaporation of solvent therefrom, pure solvent will flow from 42 thru the membrane ts to replenish the supply in the evaporator.

In Figure '7 is shown a system in which the re-. 7

frigerant in the evaporator 86 is heavier than the propelling solvent from the boiler. The entraining and the entrained fluids are condensed and collect in the receiver, the refrigerant d8 7 collecting at the bottom of the receiver and the entraining fluid 41 rising above the heavier refrigerant. A semi-permeable membrane 49 separates the pure solvent liquid from the solution in the boiler. A pipe 56 connects the receiver with the evaporator. Flow of refrigerant thru the pipe 50 is controlled by a valve which is operated by a float 52. The float is heavier than the pure solvent 41 but is lighter than the refrigerant 46 so that as liquid refrigerant 46 collects in the receiver the float rises and allows refrigerant to now to the evaporator. There is of course a greater pressure in the receiver than in the evaporator so that refrigerant will be forced thru pipe 50 as soon as the valve 5| is opened. The valve will close as soon as the level of the refrigerant falls thereby preventing the passage of the liquid 4! to the evaporator. This system makes it possible to use two liquids so as to take advantage of the best properties of a solution for the boiler and a different liquid as a refrigerant and to return each to its proper vessel in a continuous cycle of operation. The pure solvent 41 may be water and the heavier refrigerant 66 may be dibromobenzene (either ortho or meta) having a specific gravity of about 1.95 or difiuorodichloromethane, known in the trade as freon and having a specific gravity of about 1.49. Both of these refrigerants are insoluble in water.

Figure 8 shows a system in which a pressure operated valve controls passage of solvent liquid to the evaporator. Numerals 53, 54 and 55 denote a boiler, an evaporator and a receiver respectively. A semi-permeable membrane 56 separates the pure solvent in the receiver from the solution in the boiler. Numeral 51 is a heater which generates vapor which issues thru nozzle 63 and draws evaporated refrigerant from the evaporator thru pipe 64, the entraining and the entrained gases being condensed in 65. The receiver 55 communicates thru pipe 66 with a tank 58. Passage of liquid from pipe 66 to the tank 58 is controlled by a valve 60. This valve is connected to a bellows 6| the interior of which is subject thru pipe 62 to'the pressure of the entrained and entraining gases from the nozzle 63 in advance of the condenser so that the pressure in the bellows will be the same as the pressure upon the surface of the liquid in the receiver. The pressure below the valve 60 will be the same pressure plus the additional pressure of the column of liquid in pipe 66 above the level of the liquid in the tank 58. It will be apparent, therefore, that the valve 66 will open only when there is a column of liquid in the pipe 66. This will insure that no gas will pass from the receiver to the evaporator. From the tank 58 refrigerant flows thru pipe 59 into the evaporator.

It will be obvious to those skilled in the artthat many changes may be made in the invention without departing from the spirit thereof, we therefore do not limit ourselves to the invention as shown in the drawings and described in the specification but only as set forth in the appended claims.

What we claim is:

l. A refrigerating system of the jet compressor type which comprises a boiler containing a solution of a non-volatile solute in a volatile solvent, an aspirator, an evaporator, means for supplying a vapor of said solvent from said solution at high velocity for operating said aspirator to draw refrigerant from said evaporator, a condenser and a receiver positioned to receive the fluid delivered thereto by said aspirator, and a semi-permeable membrane separating the liquid solvent in the receiver from the solution in the boiler.

2. A refrigerator of the jet compressor type comprising a boiler containing a solution of a solvent and a non-volatile solute, a jet pump, means for supplying vapor at high velocity from said boiler to said jet pump, an evaporator, a connection from the suction of said jet pump to the said evaporator for drawing ofi vapor from the evaporator, a condenser and a receiver positioned to receive the fluid discharged by the said jet pump and a semi-permeable membrane separating the liquid solvent in the receiver from the solutionin the boiler for causing the pure solvent to flow by osmosis into the boiler, and gravity means for supplying pure liquid solvent to the evaporator to replace the solvent evaporated therefrom.

3. A refrigerator comprising an evaporator, a boiler, a jet compressor operated by vapor from the'boiler for drawing off refrigerant vapor from the evaporator, a condenser-receiver positioned to receive the fluid discharged by the jet compressor, the boiler having a solution'of a solvent and a non-volatile solute, thereceiver having a liquid solvent the same as that in the boiler and a semipermeable membrane separating the solvent in the receiver from the solution in the boiler for causing said pure solvent to flow by osmosis from said receiver to the boiler against the pressure in the boiler and means for supplying pure solvent to the evaporator to replace that evaporated therefrom. Q

4. A refrigerator of the jet compressor type comprising a boiler, an evaporator, a condenserreceiver, the boiler having a body of liquid consisting of a volatile solvent and a non-volatile solute, the evaporator having aliquid refrigerant of the same elements as those in the solution in the boiler but being a more concentrated solution, a semi-permeable membrane separating the solution in the boiler from the solution in the evaporator, and an aspirator operated by vapor from the boiler for withdrawing evaporated refrigerant from the evaporator and delivering it to the condenser-receiver.

5. A refrigerator of the jet compressor type comprising a boiler, an evaporator, a condenserreceiver, said boiler having therein a body of refrigerant solution consisting of a solvent and a non-volatile substance dissolved therein, a; semipermeable membrane separating the said solution from pure solventin the receiver, said evaporator having a body of refrigerant therein of a density different from that in the boiler, means for controlling the flow of refrigerant from the receiver to the evaporator, said means being operative to permit only the liquid refrigerant which came from the evaporator to return back to the evaporator.

6. A refrigerator of the jet compressor type 0 comprising a boiler, an evaporator. a condenser, a receiver, said boiler having a solution of a refrigerant and a non-volatile solute dissolved therein, means for boiling of! vapor from the boiler and delivering it to the jet compressor to draw off evaporated refrigerant from the evaporator and deliver it to the condenser and receiver, a semi-permeable membrane separating the solution in the boiler from the body of pure solvent in the receiver, means for supplying solvent from the receiver to the evaporator, a valve in control of said last named means, said valve being operated by hydrostatic pressure when a predetep mined amount of liquid solvent has accumulated in the receiver to permit passage to the evaporator of only liquid solvent.

7. In a refrigerating system, the method of clrculating the refrigerant fluids which comprises 5 heating a solution having a non-volatile solute disolved in a pure solvent to drive off the solvent, utilizing the solvent vapor thus driven off to circulate other refrigerant fluid, condensing the combined fluids, separating from the mixture the 10 pure solvent resulting from the condensation by a semi-permeable membrane to cause the pure solvent to flow by osmosis to the body of the solution from which it was drawn ofi. L

8. The method of refrigerai ion which comprises 15 circulating the vapor from a solution and causing said circulation to create a regionof low pressure above the surface of a solution of greater concentration to cause the solvent of said second solution to evaporate more rapidly, condens- 20 ing said vapors and returning the liquid resulting from the condensation to its starting points by causing it to flow by osmosis thru semi-permeable membranes.

9. In a refrigerating system, the method of circulating a refrigerant which comprises heating a solution having a non-volatile solute dissolved in a solvent to drive ofi solvent vapor, utilizing the solvent vapor thus driven off to draw vapor of a refrigerant from a body of the refrigerant, condensing the solvent vapor and the refrigerant vapor and effecting return of the condensed solvent to the solution by the osmotic action of a semi-permeable membrane positioned between the condensed solvent and the solution.

10. A method as defined in claim 9 in which the refrigerant and the solvent are identical.

11. A method as defined in claim 9 in which the refrigerant and the solvent are liquids of different densities.

KEMPER P. BRACE. ROBERT B. P. CRAWFORD. 

